NASA’s Kepler Telescope has just returned the final batch of data from its primary mission and it includes 10 new Earth-sized worlds in the habitable zone of their star.

This final catalogue, which includes 219 planet candidates, was part of Kepler’s original four-year mission looking at a portion of the sky known as Cygnus. This long observing time allowed it to find some worlds akin to our own, with similar sizes and orbital periods around their stars.

“The Kepler data set is unique, as it is the only one containing a population of these near Earth-analogs – planets with roughly the same size and orbit as Earth,” said Mario Perez, Kepler program scientist in the Astrophysics Division of NASA’s Science Mission Directorate, in a press briefing. “Understanding their frequency in the galaxy will help inform the design of future NASA missions to directly image another Earth.”

The total count of planet candidates now stands at 4,034 found by Kepler, with 2,335 verified as exoplanets. Of these, about 49 are Earth-sized and in the habitable zone of their stars, 30 of which have been verified. And there may be some more in the data.

Within that list of Earth analogues, perhaps the most intriguing is a world called "7711". This world is about 1.3 times the size of ours, but orbits a similar star in a similar position, so it receives a similar amount of energy. Future telescopes like the James Webb Space Telescope (JWST) could allow us to study worlds like this in more detail.

It was also announced that astronomers have found an intriguing division between two types of planet. They found that rocky Earth-size planets and gaseous planets smaller than Neptune, called mini-Neptunes, have a gap between them. Few to no planets were found to form between 1.5 and 2 Earth radii.

“Finding two distinct groups of exoplanets is like discovering mammals and lizards make up distinct branches of a family tree,” Benjamin Fulton from the University of Hawaii in Manoa, who led this study into planet sizes, said during a press briefing.